The detailed structure of eutherian sperm chromosomes will be investigated using physical methods including circular dichroism spectroscopy, linear dichroism spectroscopy, reflectance spectroscopy and Raman spectroscopy in conjunction with light and electron microscopic techniques. These studies are carried out on chromatin material released from intact sperm cells by the action of disulfide reductive reagents at low concentration. This material appears to be quite native and to contain a high degree of high level structural ordering.